Dual-ratio tuning mechanism



April 27, 1937. J, H, TEAF 2,078,427

DUAL RATIO TUNING MECHANISM Filed April so, 1935 /NVEN TOP WitnessesJohn H. Tea 62W! a] v. I r

. HTTORNEY I 1. mac: HHC ELEM'CN l S Patented Apr. 27, 1937 Search RooUNITED STATES PATENT OFFICE DUAL-RATIO TUNING MECHANISM John H. .Teaf,Camden, N. J., assignor to Radio Corporation of America, a corporationof Delaware Application April 30, 1935, Serial No. 19,033

3 Claims.

My invention relates to improvements in dualratio tuning mechanism forall-wave radio receivers.

In the conventional all-wave radio receivers, provision has been madefor obtaining different drive ratiosbetween the manually operable shaftor shafts for tuning the gang condenser. For this purpose, it has beenproposed to provide two tuning knobs on the front panel of the set andindependent driving connections to the tunin condenser, construction andrelations being such that upon manual rotation of one knob through agiven angle, the condenser shaft is rotated through a relatively largeangle for coarse tuning, while uponmanual rotation of the other knobthrough the same angle, the condenser shaft is rotated through only arelatively small angle for fine tuning. A tuning mechanism of thisgeneral type is disclosed in the co-pending application of William E.Newman, Serial No. 755,337, filed November 30, 1934.

For the purpose of avoiding the use of two separate tuning knobs inmechanism of the general type referred to, it has been proposed toemploy a single tuning knob fixed to a tuning shaft which has a slightamount of axial movement, and through which both the high-ratio and thelowratio driving connections are made to the condenser shaft. Thearrangement and construction is such that by pushing the tuning knob in,connection to the condenser shaft at one of the drive ratios is made,while upon pulling out upon the tuning knob connection to the condensershaft is made at the other drive ratio. A tuning device of this generaltype is disclosed in the co pending application by William E. Newman,Serial No. 722,849, filed April 28, 1934.

While the various constructions for dual-ratio tuning mechanism proposedheretofore have been satisfactory in operation, they have requiredeither the use of separate tuning knobs for the different ratios or, inthe mechanism employing a single tuning knob, the use of some form of,

55 push-pull action or other movement of the single tuning knob otherthan rotation of the same about a fixed axis.

Another object of my invention is to provide improved tuning mechanismof the character referred to which is relatively inexpensive and whichavoids the various manufacturing difliculties of the constructionsproposed heretofore.

Other objects and advantages will hereinafter appear.

In accordance with my invention, dual-ratio driving connections are madebetween a single tuning shaft and an idler shaft from which thecondenser shaft is driven. There is a certain amount of free play in thedriving connection at the low-ratio, so that the tuning shaft can berotated through almost a complete revolution to drive the condensershaft through only the highratio connection, before the low-ratioconnection begins to become effective. Upon continuing rotation of thetuning shaft in either direction beyond the limits of the angle for freeplay in the driving connection at the low ratio, this connection becomeseffective, and the driving connection at the high ratio is releasedautomatically by a clutch device associated with the tuning shaft. Thecondenser shaft is then driven from the tuning shaft at the low ratiofor coarse tuning. In tuning to any desired station, the single tuningknob is first rotated to adjust the condenser approximately to afrequency slightly beyond that of the station, after which the tuningknob is rotated in the reverse direction, whereupon the condenser isdriven through the high ratio for fine tuning to the desired frequency.

My invention resides in the improved construction of the characterhereinafter described and claimed.

For the purpose of illustrating my invention, an embodiment thereof isshown in the drawing,

wherein V Figure 1 is a side elevational view of tuning mechanismconstructed and operating in accordance with my invention;

Fig. 2 is an enlarged, detailed, fragmentary view, taken from Fig. 1;

Fig. 3 is a sectional view, the section being taken on the line 3-3 inFig. 2;

Fig. 4 is a sectional view, the section being taken on the line 44 inFig. 2; and

'Fig. 5 is a front elevation view, partly in section, the section beingtaken on the line 5-5 in prises a single tuning shaft I0 journalled atone end thereof in the frame members l2 and I4 and provided at its otherend with a knob I 6, an idler shaft I 8 journalled in the frame members,and a third shaft 26 coupled to the shaft of a gang condenserrepresented at 22.

The idler shaft I8 is driven from the tuning shaft at a relatively highratio by a connection comprising a disc 23 fixed on the shaft l8 andcomplementary discs 24 and 25 associated with the tuning shaft l0 andengaging respectively opposite faces of the disc 23 at the edge of thelatter, as more clearly shown in Fig. 2. The disc 25 is fixed on theshaft 10, while the disc 24 is slidable along this shaft and is urgedtoward the disc 25 by a spring 26 compressed between the disc 24 and awasher 28. The washer 28 is loose on the shaft 10, and is backed by asplit collar 36 fixed against axial movement on this shaft by beingsnapped in place thereon in an annular groove in the shaft, as shownmore clearly in Fig. 4.

The idler shaft 18 is driven from the tuning shaft ID at the relativelylow ratio by a connection comprising a gear member 32 loose on the shaftIll and meshing with a pinion 34 fixed on the shaft l8. For the purposeof causing the gear 32 to rotate with the shaft 3, it is provided with aprojection 36 disposed to be engaged by an arm 38 which is loose on thisshaft but is connected for rotation with the disc 25 by pins 40. Thepins 46 extend through and have a sliding fit in the disc 25 fixed tothe shaft Ill. One end of each of the pins 46 is disposed in a V-shapenotch 42 in the member 38, and each pin is held in this position byengagement of its other end with the adjacent face of the disc 24. Thecondenser shaft 20 is driven from the idler shaft l8 at a relativelyhigh ratio by a connection comprising a disc 44 fixed to the shaft 20and having its edge disposed between complementary discs 46 and 48 onthe shaft I8. The disc 46 is fixed for rotation with the disc 23, whilethe disc 48 is loose on the shaft l8. A spring 50, compressed betweenthe disc 48 and a washer 52 on the shaft l8, operates to maintainfrictional driving engagement between opposite faces of the disc 44 andthe respective faces of the discs 46 and 48.

An indication of the frequency or station to which the receiver is tunedis provided by a pointer 54 and a fixed dial 56 provided with the scales58 and 60 concentric about its center. The pointer 54 is fixed on theend of a spindle 62 connected by rotation with the condenser shaft 20and extending through a hollow shaft or bushing 64 to which a vernierpointer 66 is fixed.

In operation, the vernier pointer 66 rotates over a vernier scale 68through an angle of about 120 while the pointer 54 rotates over thescales 58 and 60 through an angle of about 10, as represented in Fig. 5.For this purpose, a pinion l0, fixed on the bushing 64, meshes with anidler gear 12 fixed for rotation with a pinion 14 which meshes with agear 16 fixed for rotation with the condenser shaft 20.

In operation, the tuning knob l6 can be turned through almost onecomplete revolution before the arm 38 engages the projection 36 to carrythe gear along with the arm as the shaft l6 continues to be rotated. Theidler shaft I8 is then driven from the tuning shaft ID at the low ratio,through the gear 32 and the associated pinion 34. As the arm 38 engagesthe projection 36, however, there will be a slight resistance to coninued rotation of the shaft III on account of the frictional engagementof the disc 44 with the discs 46 and 48 under the action of the spring56. This resistance is sufllcient to force the pins 40 to the right, asviewed in Fig. 2, by the cam action provided by the inclined faces ofthe notches 42. In this way, the disc 24 is forced to the rightsufliciently, against the action of the spring 26, to release the edgeof the disc 23 from its full, normal frictional driving engagement withthe adjacent faces of the discs 24 and 25. The high-ratio drivingconnection between the shafts l0 and I8 is thereby automaticallyreleased when the shaft I0 is rotated to cause the arm 38 to engage theprojection 36 from either side thereof. When the condenser shaft 26 isbeing driven through the low-ratio drive comprising the gear 32 and theassociated pinion 34, therefore, the operator does not have to overcomeany substantial drag which would otherwise be caused by the normalfriction or engagement between the parts comprising the high-ratiodriving connection.

When tuning to any station, the operator rotates the knob l6 in theproper direction to place the pointer 54 in a position, along the scaleon which he is working, slightly beyond the point on the scale at whichhe estimates the station will be in tune, during which time the arm 38is engaging the projection 36 whereby the condenser shaft is beingdriven through the low-ratio drive provided by the gear 32 and thepinion 34. The knob I6 is then rotating in the reverse direction,whereupon the arm 38 recedes from the projection 36 so that the pins 46can again slide fully into the recesses 42 and the spring 26 causefrictional driving engagement of the discs 24 and 25 with the disc 23.The condenser shaft 20 is then driven from the tuning shaft l0 throughthe high-ratio drive provided by the discs 23, 24 and 25, and by nowobserving the position of the vernier pointer 66, the operator canlocate exactly the frequency or station to which he wants to tune.

From the foregoing it will be seen that I have provided improved tuningmechanism in which provision is made for dual-ratio tuning by rotationof a single tuning knob, the action being such that the condenser shaftis rotated through a high-ratio connection for fine tuning duringrotation of the tuning shaft through a range of approximately 360, afterwhich the condenser shaft is rotated through a low-ratio connection forcoarse tuning. Furthermore, it will be seen that my improvedconstruction is relatively simple and inexpensive.

Various modifications, within the conception of those skilled in theart, are possible without I departing from the spirit of my invention orthe scope of the claims.

I claim as my invention:

1. Tuning mechanism for a radio receiver comprising a tuning shaft, anidler shaft, a third shaft, means for driving the idler shaft from thetuning shaft at a relatively high ratio, means for driving the idlershaft from the tuning shaft at a relatively low ratio and comprising amember loose on the tuning shaft, an element carried by the tuning shaftfor rotating said member with the tuning shaft, said element beingfreely movable with respect to said member through a given angle, meansfor releasing said firstnamed means when the tuning shaft is rotated ineither direction to bring said element into position to rotate saidmember, and means for driving the third shaft from the idler shaft.

2. Tuning mechanism for a radio receiver comprising a tuning shaft, anidler shaft. a third shaft, means for driving the idler shaft from thetuning shaft at a relatively high ratio and comprising complementarydiscs carried by the tuning shaft and a disc fixed on the idler shaftand having its edge disposed between the complementary discs, springmeans for urging said complementary discs together into frictionaldriving engagement with said third-named disc, means for driving theidler shaft from the tuning shaft at a relatively low ratio andcomprising a member loose on the tuning shaft, an element carried by thetuning shaft for rotating said member with the tuning shaft, saidelement being freely movable with respect to said member through a givenangle, means associated with said element and one of said complementarydiscs for releasing said complementary discs from frictional drivingengagement with said third-named disc when said element is moved throughsaid angle, and means for driving the third shaft from the idler shaft.

3. Tuning mechanism for a radio receiver comprising a tuning shaft, asecond shaft, means for driving the second shaft from the tuning shaftat a relatively low ratio comprising a gear loose on'the tuning shaftand a pinion fixed on the second shaft and meshing with said gear, meansfor driving the second shaft from the tuning shaft at a relatively highratio comprising a pair of complementary discs carried by the tuningshaft and a third disc fixed on the second shaft and having its edgedisposed between said pair of discs, spring means for urging saidcomplementary discs together, said gear being provided with aprojection, an arm carried by the tuning shaft and arranged to engagesaid projection to rotate said gear, and means connecting said arm toone of said complementary discs for rotation therewith and operable tospread said complementary discs apart as the tuning shaft is rotated ineither direction to cause rotation of said gear by said am.

JOHN H. TEAF.

